The present invention relates to a device for use to diagnose wear of piston rings which are used in diesel engines installed on vessels or motor-vehicles, and such industrial machines as compressors etc., and a diagnostic procedure therefor.
Traditionally, it has been a common procedure to check the amount of wear on a piston ring which used in an engine by withdrawing the ring while the engine is inoperative and then measuring wear surface thickness, or alternatively in two-cycle engines it has been only estimated by an operator making a visual inspection of the clearance between opposite engaging end portions of the piston ring by looking through a scavenging port when such an access to the opposite engaging end portions is allowed for him by a casual chance. These prior art procedures, however, have a problem in that they can be taken only when the engine remains inoperative, and in addition require very labor-intensive work.
Piston rings are used in reciprocating engines tend to be worn out easily or excessively, as a result of their sliding movement inside the cylinder. As the wear of the piston rings increase, the engine output decreases to result in engine troubles such as breakage and seizure etc., of the piston ring. For this reason it is very convenient if the replacement of the piston ring may be made prior to the occurrence of such engine trouble. It is thus needed to estimate the amount of wear of piston rings. In particular, with the trend of requirement for higher engine outputs, piston rings experience a greater accelerated rate of wear than ever, and accordingly it is often the case that a wear resistant material is coated onto the top ring, and still further onto the second ring. In such a case, the effective life of a piston ring can be determined by knowing the time when the wear resistant material has been worn out to expose its outer surface, and so it would be very convenient if the wear amount of the coating material can be determined precisely.
One example of traditional diesel engines is shown in FIG. 17 wherein the combustion chamber in the traditional diesel engines is shown in a cross-sectional view.
In this drawing, there are shown a pistol 01, a cylinder liner 02, a cylinder cover 03, a combustion chamber 04, an exhaust valve 05, a fuel valve 06, and piston rings 07 (including a top ring 07a, a second ring 07b, a third ring 07c and an end ring 07d). The wear of a traditional piston ring has been checked visually in accordance with a procedure wherein the piston ring 07 is withdrawn, for example, while the vessel is in a dockyard for repairing etc., and the thickness of the ring 07 surface is measured, or alternatively a clearance between opposite engaging end portions of the ring 07 are visually checked by looking through a scavenging port.
On the other hand, in traditional diesel engines, fuel is burned after being injected from the fuel valve 06 into the combustion chamber 04 when the piston reaches at around top dead center, and the internal pressure is elevated under such energy, thereby causing the piston 01 to move downwardly to rotate the crank shaft (not shown), and the piston returns back to its top dead center under inertia force.
Diesel engines are operated by repeating this operational cycle, and this operational movement causes the piston ring 07 attached on the outer surface of the piston 01 to slide relative to the cylinder liner 02. They thus wear out and sometimes cause several disadvantage such as abnormal wear, when adverse factors are present such as imperfect lubrication, metal-to-metal contact between components, and the development of corrosion and entrapment of dust etc., Excessive wear of the piston ring can cause adverse effects such as engine output reduction, cylinder breakage, and liners seizure etc., and a serious trouble must be forestalled by keeping a constant watch of the state of wear. Moreover, if the amount of wear of piston rings can be constantly monitored, a time for the replacement of the piston rings may be determined in advance, and any worn part may be replaced immediately upon the ship entering into the dockyard for repair etc., for example, and thus a substantial economic merit may be derived.
However, in accordance with the prior technique for checking the wear amount of piston rings, the procedure step for withdrawing the piston and subsequentially measuring its reduction in surface thickness, or alternatively visually checking the opposite engaging end portions of the ring by an operator looking through the scavenging port has been carried out only when the ship enters into the dockyard for repair, or when the machine is transported into a mill, as above-described, and therefore a substantial labor work has been needed. Moreover, the interval of time between the frequency of checks to be taken is long, and so it was problematic that a suitable preventive measure might not be taken timely against excessive wear of the piston ring.